FI86879C - TILL GEL BRINGADE VATTENHALTIGA BLANDNINGAR - Google Patents

Abstract

Disclosed are gelled compositions in fresh water or brine solution, containing a polymer selected from the group consisting of water-soluble anionic or nonionic polymers capable of gelling in the presene of a gelling agent characterized in that the gelling agent is a water-soluble cationic poly(N-alkyldiallylamine)-epihalohydrin resin in an amount sufficient to cause a gel to form. The compositions are useful in the recovery of oil and gas by fracturing and as a matrix plugging agent in enhanced oil recovery.

Description

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AQUEOUS MIXTURES GELED

The invention relates to thickened mixtures formed of either an anionic water-soluble polymer or a non-ionic water-soluble polymer and a water-soluble cationic resin, which are suitable for oil and gas recovery by fracturing and as tapping agents matrices for enhancing oil recovery.

oil and gas are usually found in porous or permeable underground formations. After perforation, the oil and gas in the pores are displaced into the coran hole by a variety of methods known in the art. however, oil and gas production may be hampered by the fact that the drilling fluids block the channels through which the oil and gas should flow into the borehole, or by the insufficient number of flow channels for the flow of oil and gas. Such oil well formations are said to have low permeability.

A well-established method of producing oil from a low-permeability source is hydraulic fracturing. In this method, a suitable breaking liquid is injected into the formation at a pressure sufficient to break the formation. The fracture thus obtained includes passageways along which oil and gas can flow into the borehole. The main constituents of current fractional fluids are water-soluble polymers and polyvalent metal salts and metal complexes of organic compounds. The polyvalent metal ion crosslinks with the water-soluble polymer to form a crosslinked polymer gel. Fracturing fluids usually contain propellants that keep the fracture supported after the pressure drops. This crosslinked polymer gel suspends sand, peanut shell pieces, glass beads, aluminum pellets, or other propellants as the liquid migrates to break.

When injecting a liquid into a source formation, the fracture must have and maintain the properties that give the fractures the required length and width. This is called fracture fluid efficiency. These properties are related to the fluid loss properties and viscosity of that fluid. One way to minimize water loss to borehole walls and rupture is to increase the viscosity of the fracture fluid.

Water-soluble polymers have previously been used to increase the viscosity of fracturing fluids. However, many of these polymers dissolve so rapidly that they tend to agglomerate upon mixing with water. Usually, such agglomeration is prevented by lightly crosslinking the polymers with small amounts of glyoxal, which affects the initial water solubility of the polymer, but not its final water solubility. Another way to prevent agglomeration is to blend with the polymers of U.S. Pat. No. 4,487,866, certain cationic or amphoteric polymers, such as a quaternary salt of poly (diallyldimethylamine), so as to form a water-soluble complex which dissolves more slowly, i.e. over a longer period of time, than the anionic and cationic polymers dissociate. The viscosity of such solutions is usually 30 to 100 cps. Water-insoluble gels can be prepared from such solutions by adding suitable crosslinking agents.

Water-insoluble gels are the most up-to-date breaking liquids. These gels are also prepared by crosslinking water-soluble polymers with polyvalent metals that form metal coordination bonds with the polymers, as described in U.S. Pat. 4,001,286 and 4,043,921 are described.

However, none of these materials provide gelled mixtures with sufficient gel strength and thermal stability to withstand the various conditions to which the fracturing fluids and tapping matrices are subjected.

3,86879

The present invention relates to a water-insoluble gelled mixture made in fresh or salt water and containing either a water-soluble anionic or a water-soluble nonionic polymer in an amount of 0.1% to 1.0%, which gels in the presence of a gelling agent.

The invention is characterized in that for the recovery of oil and gas, the gelling agent is a water-soluble cationic poly (N-alkyl diallylamine) epihalohydrin resin used for gel formation from 0.1% to 1.0%.

The time that a gelled polymer solution is able to maintain its uniformity depends on the depth of the source and the thermal stability of the gel at that depth. The temperature of the source demo formation is a function of depth. The deeper the source, the higher the temperature at the bottom of the source. For example, a typical temperature at the bottom of a 600 m (2000 ft) deep source is 32 to 3 3 ° C (89 to 91 ° F), while the temperature at the bottom of a 3000 m (10,000 ft) deep source is in the range of 61 to 93 ° C (141 to 200 ° F) and the 5400 m (18,000 ft) deep hole bottom temperature is in the range of 93 to 195 ° C (199 to 385 ° F). Currently, most boreholes are less than 3,000 m (10,000 ft) deep.

The thermal stability of a crosslinked polymer gel depends on the bond strength of the bridges and the durability of the polymer backbone. One way to strengthen bridge bonds is to use crosslinking agents that bind covalently to the polymer backbone instead of the usual metal coordination bonds. The excellent gel strength of the gelled compositions of this invention is believed to be due to the cationic poly (N-alkyldiallylamine) epihalohydrin resin of the invention covalently bonding to an anionic or nonionic water-soluble polymer, thereby providing stronger bonds.

Preferably, in a freshwater or saline solution at a pH above 10, a water-thickening amount of an anionic water-soluble polymer which may be carboxymethylcellulose, carboxymethylhydroxyethylcellulose, carboxymethyl guar, carboxymethylhydroxyethyl guar about 90%, or a nonionic water-soluble polymer which may be polyacrylamide, polyacrylonitrile, polyvinylpyrrolidone, copolymer of acrylamide, hydroxyethylcellulose, methylcellulose, methylhydroxyethylcellulose, ethylhydroxyethylcelluloxy, hydroxyhydroxyethylcellulose, ethylhydroxyethylcellulose

Preferably, in saline solutions having a salt content of about 1 to about 6%, a water-thickening amount of an anionic water-soluble polymer having carboxylate functionality and a cellulose backbone, which may be an alkali metal salt of carboxymethylcellulose or carboxymethylhydroxyethylcellulose.

Preferably, (a) a water-thickening amount of an anionic water-soluble polymer having a carboxylate functionality and a cellulose backbone, which may be a carboxymethylcellulose or carboxymethylhydroxy moiety or carboxymethylhydroxy, is used in (a) saline solutions having a salt content of about 1% to about 2%. (b) in saline solutions having a salt content of more than 2% f between neutral and pH 10, a water-thickening amount of a copolymer of sodium acrylate having an acrylate content of about 10 to about 90%.

The acrylate content of the sodium acrylate copolymers is preferably from about 10% to about 50%, especially from about 10% to about 30%.

Usually, the degree of carboxymethyl substitution (DS) is from about 0.1 to about 1.5, preferably from about 0.1 to about 1.0, except for CMC, which preferably has a degree of substitution from about 0.7 to about 0.9. DS is the average number of substituted hydroxyl groups per anhydroglucose unit of the cellulose molecule or per anhydrohexose unit of the guar molecule, depending on which anionic polymer is used. Usually, the molar degree of hydrohydroxyethyl or hydroxypropyl substitution MS is s 86879 from about 0.15 to about 3.0, preferably from about 1.0 to about 2.5, and especially from 1.5 to about 2.5. MS is the average molar amount of ethylene oxide or propylene oxide per anhydroglucose unit of the cellulose molecule or per anhydrohexose unit of the guar molecule. Suitable alkali metals include e.g. sodium and potassium. Sodium is the preferred alkali metal.

Methods for preparing these anionic cellulose and guar polymers are well known in the art. See. e.g., Whistler, R.L. and BeMiller, J.N., Industrial Gums, 310, 486-89, 649-72, 695-729 (2nd Ed. 1973).

Xanthan gum is a commercially available anionic polysaccharide that contains a carboxylate group in the polymer repeating unit. Xanthan gum is produced by fermentation of bacteria of the genus Xanthomonas campestris.

Suitable copolymers of sodium acrylate include e.g. sodium acrylate-acrylamide copolymers and sodium acrylate-methacrylamide copolymers. Sodium acrylate-acrylamide copolymer is preferred. Such copolymers usually have a molecular weight of about 50,000 to about 30,000,000. The preparation of sodium acrylate copolymers is well known in the art.

Nonionic polymers useful in the compositions of this invention include e.g. polyacrylamides, polyacrylonitrile, polyvinylpyrrolidone, acrylamide copolymers, hydroxyethylcellulose (HEC), methylcellulose (MC), methylhydroxyethylcellulose (MHEC), hydroxyethyl (HEC), ethylhydroxyethylcellulose (EHEC), hydroxy .

Nonionic acrylamide polymers and copolymers, polyacrylonitrile, polyacrylic acid and polyvinylpyrrolidone can be prepared by methods known in the art or can be purchased commercially. These polymers usually have a molecular weight of about 50,000 to about 30,000,000.

6 86879

The hydroxyethyl or hydroxypropyl MS of the cellulose and guarethers is from about 0.15 to about 3.0, preferably from 0.2 to about 2.5. The methyl and ethyl DS of these ethers are usually from about 0.1 to about 1.0.

Methods for preparing HEC, MC, MHEC, EHEC, HPHEC, HEG, and HPG are known in the art; e.g., Whistler, R.L. and BeMiller, J.N., Industrial Gums, 310, 620-22, 652, (2nd. Ed. 1973).

The water-soluble cationic poly (diallylamine) epichlorohydrin resins of this invention usually have a molecular weight of 100 to 20,000,000, preferably 50,000 to 10,000,000, and especially 50,000 to 3,000,000. The activated form of these resins, which occurs at a pH of at least 8 are believed to contain repeating units of formula I or formula II: X ° \ R CH2-CH - CH2 »2C <JH2 --H2c-HC-CH-CH2-- _ _ n .0 R ^, ch2-cä —— ^: h2 / X x- 11 »2 <j - ^ XCH-CH2-- __ CH2 n wherein R is C1-4 alkyl, X is a halide anion and n is an integer sufficient to give the resin a molecular weight from about 100 to about 20,000,000, or mixtures of formulas I and II. Repeated 7,86879 units may have some short side chains due to the ability of the epoxy group to form chains.

Suitable groups R include e.g. methyl, ethyl, propyl, isopropyl and butyl. The methyl group is a preferred alkyl group. The halide ion is usually chloride or bromide. The preferred water-soluble cationic resin to be used in accordance with the present invention is poly (N-methyldiallylamine) epichlorohydrin.

In the acidic pH range, i.e. below pH 5, the repeating units of the resins are believed to be of formula III or IV.

OH

R CH "-CH-CH.X

\ / N + / \ H2c ch2 --H2C-HC-CH-CHj-- _ n

OH

R CH = - <L-CH-X

\ / N + / \ H2C CHj --H <* CH-CH, -

V

_ __J n 86879 wherein R, X and n are as defined above, or mixtures of formulas III and IV.

The resins are prepared by polymerizing a hydrogen halide salt of N-alkyldiallylamine and reacting the poly (N-alkyldiallylamine) thus formed with epihalohydrin, especially epichlorohydrin, according to methods known in the art. See. e.g., U.S. Pat. 3,700,623 and 3,833,531, which are incorporated herein by reference. The total dry matter content of the resin solution thus obtained is generally from about 20% to about 21% before dilution.

Poly (N-alkyldiallylamine) epihalohydrin resins are prepared as aqueous solutions having a pH of about 7 to about 9.5, and the resins contain structures of formula I or II, or both, and tend to gel upon standing. The resin solutions are stabilized against gelation by adding to the aqueous solutions of the resins a sufficient amount of acid, such as hydrochloric acid, to maintain the pH at about 2, in which case the resin contains units of formula III or IV, or both. In this case, resins are referred to in the art as stabilized resins, and are usually marketed in this form. Acid-stabilized resins are reactivated prior to use by known methods so that structures I or II, or both, are recovered. Such acid-stabilized resin solutions and methods for their reactivation are described in U.S. Pat. 3,833,531. The preferred method of reactivation is to add aqueous sodium hydroxide solution.

The compositions of this invention may be prepared as fracturing fluids for use on the surface in a suitable container equipped with agitators and pumped down the borehole into the source formation using conventional equipment therefor. Mixtures can also be prepared "on the fly", i.e., while being pumped down to the source. In this case, a solution of the anionic or nonionic polymer containing the support is prepared in the tank through the wellbore of the source and the pumping of the solution into the hole is started. The cationic resin solution in activated form is prepared in a separate tank and passed to a solution of anionic or nonionic polymer containing a support from a suitable junction located a few meters downstream of the anionic or nonionic polymer mixing tank. The rate at which the components are introduced into the line depends on the pumping rate of the particular mixture of this invention, which is known to those skilled in the art. Other methods for combining the ingredients of such fracturing fluids are also known to those skilled in the art.

The compositions of this invention can also be mixed into solutions on the surface of the earth to form dilute gels that can be easily pumped. The heat of the borehole, especially at the bottom of the borehole, activates the crosslinking reaction. For low fracture, the mixture or separate polymer and resin solutions can be heated prior to pumping.

At pH values above 10, all of the anionic and nonionic polymers of this invention form gels as solutions in both freshwater and saline.

Under acidic conditions, in saline solutions with a salt content of about 1 to about 6%, only anionic water-soluble polymers with carboxylate functionality and a cellulose backbone gel.

At a pH between neutral and about 10, only (1) anionic water-soluble polymers having carboxylate functionality and a cellulose backbone gel at a salt content of about 1 to about 5%, and (2) copolymers of sodium acrylate and ethylenically unsaturated monomer having about acrylate 10 to about 90%, gelling at more than 2% salinity.

Thus, at certain pH values, salinity may be a critical factor for gel formation.

10 86879

The preferred polymer is CMHEC. It forms gels with the cationic resins useful in this invention at all pH values in both fresh and salt water.

The amount of anionic or nonionic polymer used in the practice of this invention will vary depending on the viscosity and purity of the polymer. Generally, a water-thickening amount is added, i.e., an amount that substantially thickens the water. Usually the amount is from about 0.1 to about 1.0%, preferably from 0.4 to about 0.8%.

The concentration of the cationic resin varies depending on the molecular weight of the resin. Usually the amount is about 0.1 to about 1%, preferably 0.2 to about 0.4%.

The invention is illustrated by the following examples. All percentages are by weight unless otherwise indicated.

Example 1 This example describes a gelled aqueous mixture according to the invention and its preparation.

2 g of carboxymethylhydroxyethylcellulose having a carboxymethyl DS of 0.4 and a hydroxyethyl MS of 2.0 and 4 g of KCl in 200 g of water are introduced into a mixing vessel equipped with a stirrer. Mixing is started and continued throughout the preparation. The pH of the solution is adjusted to 6 by adding a suitable reagent, i.e. either sodium hydroxide or hydrochloric acid.

An acid-stabilized solution of poly (N-methyldiallylamine) epi-chlorohydrin resin, 12 g (5% dry matter), is activated in a separate vessel by adjusting the pH to 12 with sodium hydroxide solution. This is then added to the mixture and stirred well at 90 ° C (194 ° C). F).

The storage modulus (G ') of the gel formed in 20 minutes is 200 dynes / cm 2.

n 86879

Examples 2-86 These examples relate to embodiments of the gelled aqueous compositions of the invention.

The formulations and methods of Example 1 are used to prepare mixtures and controls, but the formulations have been modified according to Tables I to V.

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Gelled aqueous mixtures have good thermal stability, as evidenced by their decomposition temperatures TD and storage modules G '. G 'is a measure of gel strength. The storage modulus of a strong gel is about 100 dynes / cm. The sotrage modulus of a weak 2 gel is about 10 dynes / cm. Table VI shows the T and G 'values for some gels with

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certain anionic polymers have been used in the preparation at pH 3 and pH 12, and gels prepared from nonionic polymers at pH 12.

Table VI

Example No. Tn ° C (° F) G ', dyn / cm 2. - 1 - - —o ————— —- 23 95 (203) 300 30 194 (380) 400 75 183 (360 450 82 200 (392) 500 Accordingly, the present invention provides gelled aqueous compositions having good thermal stability. , and which can be used in fracturing fluids for the recovery of oil and gas from source formations.Gels can also be used as excipients to improve oil recovery and in other gas and oil recovery operations.

After reading the above description, the objects, advantages and specific embodiments of the present invention will be readily understood by those of ordinary skill in the art. Accordingly, although specific embodiments of the present invention have been described in considerable detail, changes may be made to these embodiments without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (11)

A water-insoluble gelled composition in fresh or salt water containing either a water-soluble anionic or non-ionic polymer, the amount of which is 0.1 to 1.0% and which gels in the presence of a gelling agent, characterized in that oil or gas This gelling agent is a water-soluble cationic poly (N-alkyldiallyl-amine) epihalohydrin resin used for gel formation in the amount of 0.1 - 1.0%. 2. A composition according to claim 1, gelled in fresh water at a pH above 10, characterized in that the polymer is an anionic water-soluble polymer, which may be an alkali metal salt of carboxymethylcellulose, carboxymethylhydroxyethyl cellulose, carboxymethylguanymethylhydroxyethylhydroxyethylhydroxyethyl hydroxy copolymer of sodium macrylate, whose acrylate content is approx. 10 - approx. 90%. Composition according to claim 1, gelled in fresh water at a pH above 10, characterized in that the polymer is a non-ionic water-soluble polymer which may be polyacrylamide, polyacrylonitrile, polyvinylpyrrolidone, acrylamide copolymer, hydroxyethyl cellulose, methyl cellulose, methyl cellulose, xyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl hydroxyethyl cellulose, hydroxyethyl guar and hydroxypropyl guar. 4. A composition according to claim 1, gelled in the saline solution at a pH above 10, characterized in that the polymer is an anionic water-soluble polymer, which may be an alkali metal salt of carboxymethylcellulose, carboxymethylhydroxyethyl cellulose, carboxymethylguanyl carboxymethylhydroxyethylgluxymethylhydroxyethylhydroxyethylhydroxyethylhydroxyethylhydroxyethylhydroxyethylguy sodium acrylate copolymer, the acrylate content of which is approx. 10 - approx. 90%. Composition according to claim 1, gelled in the saline solution in the PH value above 10, characterized in that the polymer 86879 is a nonionic water-soluble polymer which may be polyacrylamide, polyacrylonitrile, polyvinylpyrrolidone, acrylamide copolymer, hydroxyethyl cellulose, methyl cellulose, -xyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl hydroxyethyl cellulose, hydroxyethyl guar and hydroxypropyl guar. Composition according to claim 1, gelled in the saline solution of an acidic PH range, characterized in that the polymer is an anionic water-soluble polymer which has carboxylate functionality and cellulose core and which can be an alkali metal salt of carboxymethyl cellulose or carboxymethyl cellulose methyl hydroxyethyl. The gel composition according to claim 6, characterized in that the salt concentration of the saline solution is approx. 1 - approx. 6%. The composition of claim 1, gelled in the saline solution having a pH of between neutral and ca. 10, characterized in that the polymer is an anionic water-soluble polymer which has carboxylate functionality and cellulose core and which can be an alkali metal salt of carboxymethyl cellulose or carboxymethyl hydroxyethyl cellulose. The gel composition according to claim 8, characterized in that the salt concentration of the saline solution is approx. 1 - approx. 5%. The composition of claim 1, gelled in the saline solution having a pH of between neutral and ca. 10, characterized in that the polymer is a copolymer of sodium acrylate, the acrylate content of which is approx. 10 - approx. 90%. The gel composition according to claim 10, characterized in that the salt concentration of the saline solution is above 2%.